JP2017529558A - Optical anti-counterfeiting element with all parallax diffraction optical variable image - Google Patents

Abstract

The invention includes a base layer and an optical assembly that at least partially covers one surface of the base layer, wherein the optical assembly exhibits a full parallax image when the optical assembly is illuminated with white light. An optical security device having a full parallax diffractive optically variable image having a microrelief structure that operates to be disclosed is disclosed. According to the present invention, a micro-relief structure can be obtained by combining phase planes, and reconstruction of an all-parallax diffraction optical variable image can be achieved under the condition of white light irradiation.

Description

  The present invention relates to an optical counterfeit prevention technique, and more particularly to an optical security device having a total parallax diffraction optical variable image.

  Optical security elements with diffractive optical variable images (eg holograms, dynamic diffracted images, etc.) can be applied to various prints with high security and high added value such as banknotes, identification cards, product packages etc. to prevent counterfeiting. It is widely used and achieves good effects. For example, large euro banknotes employ hot stamp patches having a diffractive optically variable image, while small banknotes employ hot stamp stripes having a diffractive optically variable image. The renminbi employs a window thread with a diffractive optically variable image, except for one yuan currency. Visa, MasterCard, and UnionPay cards use hot stamp patches with diffractive optical variable images, and important Chinese materials such as ID cards, driver's licenses, passports, etc. Adopt prevention technology. At present, most banknotes, credit cards, passports, etc. in the world employ anti-counterfeiting technology for diffraction optical variable images.

  Optical variable images can reconstruct three-dimensional effects, dynamic changes, color change images, etc. under white light irradiation conditions, and also under laser irradiation or by other supplementary means (decode plate, magnifying lens, etc.) Hidden patterns, coded patterns, etc. can be reconstructed. The latter is an anti-counterfeit function for professionals and professionals, while the former is an anti-counterfeit function for the masses. The optical structure of these anti-counterfeit products is a surface relief type diffraction grating, and is generally manufactured by transferring the diffraction structure onto the base layer through a molding process.

  Prior art diffractive optically variable images can only have parallax in one direction (generally defined as the horizontal direction) and do not have parallax in the perpendicular direction (defined as the vertical direction). That is, three-dimensional and dynamic effects can be achieved only in the horizontal direction, not in the vertical direction. This is determined by the optical grating structure of the conventional diffractive optically variable image. Just by sacrificing the parallax in the vertical direction, a clear image can be obtained under the condition of white light irradiation due to strong color dispersion. Furthermore, the conventional diffraction optical variable image reconstructs the image in the direction of ± 1 level light, but does not reconstruct the image in the direction of reflected light / transmitted light (0 level).

  An object of the present invention is to provide an optical security device having an all parallax diffractive optical variable image in order to solve the problem of achieving a full parallax diffractive optical variable image under conditions of white light illumination. There is to do.

  To achieve the above object, the present invention includes a base layer and an optical assembly that at least partially covers one surface of the base layer, and includes a microrelief structure, and when the optical assembly is irradiated with white light , Providing an optical security device having a total parallax diffractive optical variable image wherein the optical assembly exhibits a total parallax image under the action of the microrelief structure.

  According to the above technical solution, the present invention obtains a micro relief structure by means of combining a phase plate and achieves reconstruction of all parallax diffractive optical variable image under white light irradiation condition .

  Other features and advantages of the present invention are described in detail in the following embodiments.

  The accompanying drawings are provided to provide a more detailed understanding of the invention, and constitute a part of this document. They are used in conjunction with the following embodiments to illustrate the invention, but should not be understood as any configuration that limits the invention. The accompanying drawings are provided to provide a further understanding of the invention, and constitute a part of this document.

FIG. 1 shows a schematic diagram of an optical security device having an all-parallax diffractive optically variable image according to the present invention. FIG. 2 is a flowchart of a method for calculating the phase of a microrelief structure according to the present invention. FIG. 3 is a schematic diagram of an optical security device having another all-parallax diffractive optically variable image according to the present invention. FIG. 4 is a schematic diagram of an optical security device having still another all-parallax diffraction optical variable image according to the present invention.

  Hereinafter, some embodiments of the present invention will be described in detail. It should be understood that the embodiments described below are to be used for explaining and interpreting the present invention and are not intended to limit the present invention.

FIG. 1 is a schematic diagram of an optical security device having an all parallax diffractive optical variable image according to the present invention. As shown in FIG. 1, the optical security device includes a base layer 101 and an optical assembly 102 that at least partially covers the surface of the base layer 101. As shown in FIG. 1, the optical assembly 102 has a microrelief structure so that the optical assembly 102 can show a full parallax image under the action of the microrelief structure when the optical assembly 102 is irradiated with white light. doing.
“Micro-relief structure” means an uneven microstructure formed on a two-dimensional surface as required. The description of “parallax image” is as follows. Since the distance between both eyes of a person is about 65 mm, the object images seen by the two eyes are slightly different, and such a difference is parallax. A parallax image can be interpreted as a series of images of an object having a constant parallax relationship shown in different viewing directions. The parallax relationship allows the parallax image to show dynamic and three-dimensional effects. The “all-parallax image” includes not only horizontal parallax but also parallax in other directions. Unlike the conventional diffraction optical variable image reconstructed by white light having only the horizontal parallax, the “all parallax diffraction optical variable image” includes the horizontal parallax and the parallax in the other direction. Means a diffractive optical variable image reconstructed by the white light it has.

  The cross-sectional shape of the microrelief unit of the microrelief structure is one of a sinusoidal shape, a Z-shape (zigzag shape), and a rectangle, or a combination of any two or three of a sinusoidal shape, a Z-shape, and a rectangle. It may be. One skilled in the art should understand that other shapes apart from these shapes are also acceptable. A “microrelief unit” is a region formed by a curve connecting adjacent minimum points or adjacent maximum points in a microrelief structure, and these curves divide the microrelief structure into a number of regions, and each region Is a microrelief unit, and all the microrelief units constitute a microrelief structure. That is, the microrelief structure is composed of a large number of microrelief units.

  The phase of the microrelief structure shown in FIG. 1 is obtained by combining phase planes, and the specific embodiment described in the combination of FIG. 2 is as follows.

  FIG. 2 is a flowchart of a method for calculating the phase of a microrelief structure according to the present invention. As shown in FIG. 2, the phase of the microrelief structure can be obtained by calculation using the following method.

  Step 201: Decompose the original image as shown in a number of image frames corresponding to different viewing directions.

  The original image can be designed by any means with full parallax dynamic and / or three-dimensional effects to be achieved. Cameras or video cameras can be used to take real images in various directions, 3DS MAX, CAD, Photoshop (registered trademark), CoreDRAW, etc. can be used for design, and images according to the corresponding viewing angle Can be output.

  Assuming there is an m × n image frame after decomposition, m and n are positive integers, and the amplitude distribution of the image frame is

であり、式中ｐ＝１，２，，・・・，ｍ、ｑ＝１，２，，・・・，ｎ、且つ、（ｘ₀,ｙ₀）は、相当する（ｃｏｒｒｅｓｐｏｎｄｉｎｇ）画像フレーム上の点を示し、伝搬ベクトルは、

Where p = 1, 2,..., M, q = 1, 2,..., N, and (x ₀ , y ₀ ) on the corresponding (corresponding) image frame. And the propagation vector is

であり、式中（ｅ_p,q）は観察方向における、相当する画像フレームの単位ベクトルであり、λは観察方向における、相当する画像フレームの光の波長である。ｍ×ｎ画像フレームにおいて、それぞれの画像フレームはＭ×Ｎ画素群であり、ＭとＮは両方とも正の整数である。

_Where (ep _{, q} ) is the unit vector of the corresponding image frame in the viewing direction, and λ is the wavelength of the light of the corresponding image frame in the viewing direction. In an m × n image frame, each image frame is a group of M × N pixels, and M and N are both positive integers.

  Step 202: Obtain the complex amplitude of the object plane according to the amplitude of the various image frames and the direction factor for the various image frames. The details are as follows. Direction factor of each image frame with one corresponding to each image frame amplitude

を掛け、得られた結果を合計して、物体面の複素振幅を得る。式中、ｒ_p,q（ｘ₀,ｙ₀）は位置ベクトルを示す。

And sum the obtained results to obtain the complex amplitude of the object plane. In the equation, r _{p, q} (x ₀ , y ₀ ) represents a position vector.

  This explanation is shown as follows.

  The complex amplitude of an image frame is

であると仮定する。式中、Ｏ_p,q（ｘ₀,ｙ₀）はある画像フレームの振幅であり、ｒ₀（ｘ₀,ｙ₀）は（ｘ₀,ｙ₀）におけるある画像フレームの位置ベクトルである。

Assume that In the equation, O _{p, q} (x ₀ , y ₀ ) is an amplitude of a certain image frame, and r ₀ (x ₀ , y ₀ ) is a position vector of the certain image frame at (x ₀ , y ₀ ).

  The complex amplitude of the object surface is

である。

It is.

  Step 203: Inverse Fresnel transform of the complex amplitude of the object plane to obtain the complex amplitude of the object light on the surface of the optical assembly 102. Since the distance between the object surface and the optical assembly 102 is small, in order to satisfy the condition of Fresnel conversion, one pixel is taken out as one unit (taking a pixel as a unit) to perform Fresnel conversion. Conversion is required M × N times.

  Step 204: Extracting the phase of the complex amplitude of the object light on the surface of the optical assembly 102 obtained after the inverse Fresnel transformation, obtaining the amplitude value of the complex amplitude as 1, keeping the phase, and the phase ψ (x of the micro relief structure , Y).

Step 205: It is determined whether or not the calculation is to be ended. If the calculation is to be ended, step 209 is executed, and if not, step 206 is executed. There are two methods for determining the condition for terminating the operation. In the first method, the complex amplitude of the reconstruction of the microrelief structure whose phase is ψ (x, y) is further calculated, and that (the same) is compared with O (x ₀ , y ₀ ) in step 202. When the error is less than a specified value (for example, 10%), the calculation is terminated. The method for calculating the error is a method well known to those skilled in the art, and since details are not necessary, it is not shown here and is omitted. In the second method, the number of cycles is set. In general, a cycle operation of 5 to 10 times can achieve an ideal effect. Therefore, the criterion for determining whether or not to end the operation may be whether or not to execute the cycle operation 5 to 10 times. For example, it can be set to 6 times.

  Step 206: Complex amplitude of microrelief structure

にあらかじめ指定された位相平面の複素振幅を掛ける。

Is multiplied by the complex amplitude of the phase plane specified in advance.

  Step 207: Fresnel transforms the result of multiplication in step 206.

  Step 208: The result obtained after the Fresnel transformation in Step 207 is decomposed into a number of image frames corresponding to various observation directions, and then the complex amplitude in each image frame is obtained as 1 in the number of image frames. Keep the phase and then multiply it by the respective amplitude of the image frame of the original image to obtain the new object plane complex amplitude and return to step 203 for cycle computation.

  Step 209: Output the result.

  Those skilled in the art should understand that in the method shown in FIG. 2, Fresnel transformation can be performed in step 203 and inverse Fresnel transformation can be performed in step 207. A person skilled in the art can obtain the phase of the microrelief structure even when performing only one cycle, but the effect may not be good. If only one cycle is to be executed, step 201 to step 208 are executed, and then step 203 to step 205 and step 209 are executed.

  The function of the phase plane is to reduce the chromatic dispersion and improve the sharpness of the reconstructed image. The method of designing the phase of the phase plane is as follows. The phase plane is divided into a large number of pixel groups, and the size and number of pixel groups match those of the pixel groups of the respective image frames of the original image. That is, the phase plane is divided into M × N pixel groups. Each pixel in the phase plane is then re-decomposed into the same number of m × n sub-pixels as many image frames decomposed from the original image. That is, each pixel is subdivided into sub-pixels. To obtain the phase of the phase plane, each subpixel is given a phase value for the direction factor of the matching image frame.

  The phase value of the phase plane can be obtained by a multiplexing method. Two examples are used as a method for obtaining the phase value of the phase plane.

First method: obtained by multiplying the absolute value of the propagation vector k _{p, q} of a number of image frames by a first constant C ₁ and then adding a _second constant C ₂ . Multiple image frames are obtained by decomposing the original image shown in step 201. This is the simplest phase plane, and the optical assembly 102 obtained by calculation with the phase plane obtained by means of this method has a rainbow effect. When it is desired to obtain a phase plane by this method, the following restrictions are imposed on the original image. The number of pixel groups that cover between the various image frames (not including pixel groups with zero saturation) should be as small as possible and the overlap rate should be less than 20%, preferably 10% Otherwise it will have a significant impact on the clarity of the online image.

The second method: the phase distribution of the phase plane corresponds to a secondary curved surface plus a constant C _3. In this case, the original image is hardly limited. The optical assembly 102 obtained by calculation with the phase plane obtained by means of this method has a decoloring effect.

The constant C ₁ in the above two methods determines the observation range of all parallax images, and the constant C ₂ and the constant C ₃ determine the forward observation direction. When the constants C ₂ and C ₃ are 0, the observation direction is the direction of the reflected light of the security device.

  The output result, that is, the phase ψ (x, y) of the micro-relief structure is a phase function of the micro-relief structure that constitutes the optical assembly 102, and is a surface type function h (x, y) of the micro-relief structure. It is in a linear relationship. Therefore, by using ψ (x, y) to control the plate making apparatus, the origin of the optical security device of the present invention can be made. Subsequently, it is processed into a product through processes such as electroforming, embossing / UV copying, coating, and slitting.

  Furthermore, the microrelief unit of each microrelief structure shown in FIG. 1 may be 0.3 μm to 10 μm, preferably 0.8 μm to 6 μm in at least one lateral direction. The at least one lateral direction is at least one direction in a plane in which the optical security device is located or a plane parallel to them, and the size of the other lateral direction is not limited. The duty ratio of the microrelief structure (the ratio of the protrusions and the total of the protrusions and the recesses) may be 0.2 to 0.8, preferably 0.35 to 0.65.

  The depth of the microrelief structure (also referred to as the size in the longitudinal direction) may be 0.02 μm to 3 μm, and preferably 0.07 μm to 1 μm. Preferably, the depth of the microrelief structure satisfies the following condition. When natural light (white light) is irradiated onto the microrelief structure, the optical security device shows a first color in the direction of transmitted light and / or reflected light, while showing a second color in the direction of diffracted light The wavelength light is constructively interfered with in the direction of transmitted light and / or reflected light so that it can. If the material constituting the optical security device does not contain a selective absorbent, the first and second colors are complementary colors.

  The “depth of the microrelief structure” means a difference in height between the adjacent maximum value and minimum value of the microrelief structure.

  FIG. 3 is a schematic diagram of an optical security device having another all-parallax diffractive optically variable image according to the present invention. As shown in FIG. 3, the optical security device may further include a replication layer 103 positioned between the base layer 101 and the optical assembly 102, wherein the first surface of the replication layer 103 is bonded to the base layer 101. The microrelief structure of the optical assembly 102 is formed on the second surface of the replication layer 103. By adding the replication layer 103 here, replication of the microrelief structure can be facilitated, and the shape of the groove formed during the manufacturing process can be made more precise.

  FIG. 4 is a schematic diagram of an optical security device having still another all-parallax diffraction optical variable image according to the present invention. As shown in FIG. 4, the optical security device may further comprise a covering layer 104, which is located on the optical assembly 102 and covers the optical assembly 102 in the same manner, ie, in a microrelief structure. The shape is used to cover the optical assembly 102 in the same way. Of course, the present invention is not limited to these. The covering layer 104 can cover the optical assembly 102 in any form. The covering layer 104 may have a single layer structure or a multilayer structure. The covering layer 104 can be patterned, and in the case of a multilayer structure, it can be patterned into a single layer, several layers, or all of them.

The material and structure of the covering layer 104 may be different. Different materials and structures can be used to form an optical security device having a full parallax diffractive optically variable image with different effects. For example, a transparent optical security device can be formed under the condition that the covering layer 104 is a single layer of a high refractive index dielectric (ZnS, TiO _2, etc.), and the covering layer 104 is a single metal layer (Al, Cu, etc.). ), A reflective optical security device can be formed, and under conditions where the cover layer 104 is a three-layer optically variable structure including a metallic reflective layer, a dielectric layer, and an absorbing layer, the optical security device is A color shift effect can be exhibited. Under this condition, different coating layer 104 thicknesses also exhibit different color effects.

  Furthermore, the optical security device according to the present invention can also include a protective layer and a release layer (not shown). Under conditions with the covering layer 104, the protective layer can be located on the covering layer 104, and under conditions without the covering layer 104, the protective layer can be located on the replication layer 103. The durability of the security device can be improved by adding a protective layer. The release layer is located between the base layer 101 and the replication layer 103. The purpose of adding the release layer is to form a hot stamp product. Of course, the present invention is not limited to these. A protective layer can be further added between the release layer and the replication layer 103. Further fluorescent material can be added to either layer so that the security device can have fluorescent properties or patterns. In order to achieve the read characteristics of the magnetic machine, a magnetic dielectric layer can be further added to either dielectric bilayer.

  The above describes a typical preferred implementation solution of the present invention. Further, those skilled in the art can understand without departing from the spirit and scope of the present invention and can make various equivalent changes or modifications. Furthermore, the technical solution obtained should also belong to the protection scope of the present invention.

  The design of all parallax diffractive optical variable image can reconstruct various image frames with natural parallax order according to the regulations, which not only provides unpredictable visual effects, but also forgery of security devices The prevention performance can also be improved. For example, the horizontal parallax can be converted into a vertical parallax image so that a full parallax dynamic and / or three-dimensional image with right-angle dynamic effects is obtained.

  It should be described that the microrelief structure provided by the present invention can be used in combination with other types of microrelief structures in the prior art (eg, holograms, dynamic diffraction graphs, etc.).

  On the other hand, preferred embodiments of the present invention are as described above, and the present invention is not limited to one of these embodiments, and those skilled in the art can change and change technical means without departing from the gist of the present invention. All these changes and changes should be considered to fall within the protection scope of the present invention.

  Furthermore, it should be appreciated that the technical features described in the above embodiments can be incorporated in any suitable manner provided there is no conflict between the technical features in the combination. To avoid unnecessary repetition of such possible combinations, it is not described here in the present invention.

  Furthermore, different embodiments of the present invention can be freely combined as necessary without departing from the spirit and gist of the present invention. However, such combinations should be considered as falling within the scope of the present invention.

DESCRIPTION OF SYMBOLS 101 Base layer 102 Optical assembly 103 Replication layer 104 Covering layer

Claims (21)

A base layer, and an optical assembly that at least partially covers one side surface of the base layer; and
Optical security having a total parallax diffractive optical variable image that includes a microrelief structure, and wherein the optical assembly exhibits a full parallax image under the action of the microrelief structure when the optical assembly is illuminated with white light device.   The optical security device according to claim 1, wherein the phase of the microrelief structure is obtained by coupling phase planes. The optical security device according to claim 1, wherein the phase of the microrelief structure is obtained by the following steps.
1) decomposing the original image as shown in a number of image frames corresponding to different viewing directions;
2) obtaining a complex amplitude of the object plane according to the amplitude of the image frame and a directional factor with respect to the image frame;
3) Extracting the phase of the complex amplitude of the object light on the surface of the optical assembly obtained after the inverse Fresnel transformation to obtain the phase of the microrelief structure by performing inverse Fresnel transformation on the complex amplitude of the object plane Step,
4) obtaining a complex amplitude of the microrelief structure according to the phase of the microrelief structure;
5) Multiplying the complex amplitude of the microrelief structure by the complex amplitude of the phase plane specified in advance, further performing Fresnel transformation, and decomposing the obtained result into a number of image frames corresponding to various observation directions; Next, in the multiple image frames, the amplitude of the complex amplitude of each of the image frames is obtained as 1, the phase is maintained, and then the amplitude of the frame of the original image is added to obtain a new complex amplitude of the object plane. 6) Inverse Fresnel transform of the new complex amplitude of the object plane to obtain the phase of the microrelief structure to obtain the complex amplitude of the object light at the surface of the optical assembly obtained after the inverse Fresnel transform. Extracting the phase of.   The optical security device according to claim 3, wherein the phase of the microrelief structure obtained by final calculation is obtained by repeating the steps 4) to 6) 5 to 10 times. The optical security device according to claim 4, wherein the phase of the phase plane is designed by the following steps.
Dividing the phase plane into a number of pixel groups having the same size and number as the pixel groups of the image frame of the original image;
Subdividing each pixel group of the phase plane into as many subpixels as a number of image frames decomposed from the original image, and to obtain the phase of the phase plane, to each subpixel, Providing a phase value for the direction factor of the matching image frame.   6. The optical security device according to claim 5, wherein the phase value of the phase plane is obtained by multiplying the absolute value of the propagation vector of a number of the image frames by a first constant and then adding a second constant. .   The optical security device according to claim 5, wherein the phase distribution of the phase plane is a quadratic surface to which a constant is added.   The size of the microrelief unit of the microrelief structure in at least one lateral direction is 0.3 μm to 10 μm, and the microrelief structure is composed of a number of the microrelief units. The optical security device according to any one of the above.   The microrelief unit size of the microrelief structure in at least one lateral direction is 0.8 μm to 6 μm, and the microrelief structure is composed of a number of microrelief units. An optical security device according to any one of the above.   The optical security device according to claim 1, wherein the microrelief structure has a duty ratio of 0.2 to 0.8.   The optical security device according to claim 1, wherein the microrelief structure has a duty ratio of 0.35 to 0.65.   The optical security device according to claim 1, wherein the depth of the microrelief structure is 0.02 μm to 3 μm.   The optical security device according to claim 1, wherein a depth of the microrelief structure is 0.07 μm to 1 μm. The optical security device according to claim 1, wherein the depth of the microrelief structure satisfies the following condition.
When the microrelief structure is irradiated with white light, the optical security device shows a first color in the direction of transmitted light and / or reflected light and a second color in the direction of diffracted light The wavelength light is constructively interfered with in the direction of transmitted and / or reflected light so that it can.   And a replication layer positioned between the base layer and the optical assembly, the first surface of the replication layer being joined to the base layer, and at least one region of the second surface of the replication layer. The optical security device according to claim 1, wherein a microrelief structure of the optical assembly is formed in the part.   The optical security device of claim 15, further comprising a covering layer positioned on the optical assembly.   The optical security device of claim 16, wherein the covering layer covers the optical assembly in the same shape.   The optical security device according to claim 16, wherein the covering layer is patterned.   17. The covering layer according to claim 16, wherein the covering layer is one of a single layer of a high refractive index dielectric, a single metal layer, or a three-layer optically variable structure including a metal reflection layer, a dielectric layer, and an absorption layer. Optical security device.   The optical security device according to claim 16, further comprising a protective layer positioned on the covering layer, and a release layer positioned between the base layer and the replication layer.   The microrelief unit of the microrelief structure is one of a sinusoidal shape, a Z-shape, and a rectangle, or a combination of any two or three of a sinusoidal shape, a Z-shape, and a rectangle. The optical security device described.

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